Synonym: Plectognathi.
Name: derived from the Greek words tetra, meaning four, odous meaning tooth.
TaxonomyHighly derived ray-finned fish.
Genera: 49 species; 10 extant.
Habitat: marine, around tropical coral reefs; some in freshwater streams and estuaries.
TaxonomyThey have no close relatives, and descend from a line of coral-dwelling species that emerged around 80 million years ago.
ZoologyFish; various bizarre forms, radical departures from the streamlined fishes, from nearly square or triangular like boxfishes, globose like pufferfishes, to laterally compressed like Filefishes and Triggerfishes; ostraciiform swimmers, slow-moving with their caudal fins; movement is usually quite precise; highly modified skeletons; lacking nasal, parietal, infraorbital, lower rib bones; bones of the jaw are modified, fused into a sort of beak; visible sutures divide the beaks into teeth; jaws are aided by powerful muscles; many have pharyngeal teeth.
Food: hard-shelled invertebrates, crustaceans, shellfish.
Fins: simple, small, rounded; pelvic fins are fused and buried; dorsal and anal fins aid in manoeuvring and stabilizing.
Gills: gill plates are covered with skin, the only gill opening a small slit above the pectoral fin.
Size: 2 cm to 3 m; up to 2 tonnes.
Defense: fortified with scales modified into strong plates or spines; tough, leathery skin; inflate their bodies by sucking water into a diverticulum of the stomach.; by tetrodotoxin, a powerful neurotoxin.
Families • Aracanidae: Deepwater boxfishes.
• Balistidae: Triggerfishes.
•
Diodontidae: Porcupinefishes; Two-toothed pufferfish.
• Molidae: Ocean sunfishes; pelagic, feed on especially jellyfish.
• Monacanthidae: Filefishes.
•
Ostraciidae: Boxfishes.
• Tetraodontidae: Pufferfishes; Four-toothed pufferfish.
• Triacanthidae: Triplespines.
• Triacanthodidae: Spikefishes.
• Triodontidae: Threetooth puffer.